Workflow database schema cannot be changed

[felix2000jp]

I believe the "UsePostgreSQL()" parameter "schemaName" does not work as intended.

Giving it a value other than the default one -"wfc" - will just break the application since the migrations will still create the tables in the default schema because the schema name is explicitly set on the migrations script.

I think removing the hard coded schema name and allowing an easier override of the WorkflowContext and the UsePostgreSQL() could fix this issue.

I can create a PR with the changes if you agree with this

[danielgerlag]

That would be great!

[franz-at-dns]

in addition, shouldn't the migration-table be created within the same scheme as the tables?
currently, the tables are created in wfc, while the migration history is created in public